Cavity enhanced droplet spectroscopy: Principles, perspectives and prospects

Symes, Rachel; Sayer, Robert M.; Reid, Jonathan P.

doi:10.1039/b313370b

Cited by 160 publications

(192 citation statements)

References 116 publications

(208 reference statements)

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“…Lasing was realized in dye-doped liquid droplets with optical excitation of dye molecules (Tzeng et al, 1984). Micro-sized liquid droplets were also used for cavity enhanced spectroscopy (Symes et al, 2004). Liquid microjet can create a continuous and stationary column of liquid with a precise control of the hydrodynamics of the jet (see Fig.…”

Section: Liquid Droplets and Microjetsmentioning

confidence: 99%

Dielectric microcavities: Model systems for wave chaos and non-Hermitian physics

2015

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Section: Liquid Droplets and Microjetsmentioning

confidence: 99%

Dielectric microcavities: Model systems for wave chaos and non-Hermitian physics

2015

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“…The internal electric field within the particle can be described by a summation of partial waves, with the weighting of one particular partial wave dominant when the particle circumference and wavelength match the resonant condition of a WGM. Thus, WGMs can be assigned a mode number (n) and a mode order (l), which describe the radial and angular variation of the light intensity within the particle (28). We use the notation Pol l n , where Pol refers to the polarization (TE or TM designates transverse electric and transverse magnetic respectively).…”

mentioning

confidence: 99%

Comparing the mechanism of water condensation and evaporation in glassy aerosol

Bones

Reid

Lienhard

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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185

255

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Atmospheric models generally assume that aerosol particles are in equilibrium with the surrounding gas phase. However, recent observations that secondary organic aerosols can exist in a glassy state have highlighted the need to more fully understand the kinetic limitations that may control water partitioning in ambient particles. Here, we explore the influence of slow water diffusion in the condensed aerosol phase on the rates of both condensation and evaporation, demonstrating that significant inhibition in mass transfer occurs for ultraviscous aerosol, not just for glassy aerosol. Using coarse mode (3-4 um radius) ternary sucrose/sodium chloride/aqueous droplets as a proxy for multicomponent ambient aerosol, we demonstrate that the timescale for particle equilibration correlates with bulk viscosity and can be ≫10 3 s. Extrapolation of these timescales to particle sizes in the accumulation mode (e.g., approximately 100 nm) by applying the Stokes-Einstein equation suggests that the kinetic limitations imposed on mass transfer of water by slow bulk phase diffusion must be more fully investigated for atmospheric aerosol. Measurements have been made on particles covering a range in dynamic viscosity from <0.1 to >10 13 Pa s. We also retrieve the radial inhomogeneities apparent in particle composition during condensation and evaporation and contrast the dynamics of slow dissolution of a viscous core into a labile shell during condensation with the slow percolation of water during evaporation through a more homogeneous viscous particle bulk.water uptake | whispering gallery modes | Raman spectroscopy | optical tweezers | viscous aerosol A tmospheric aerosol particles are typically complex mixtures of organic and inorganic species with correspondingly complex equilibria and temporal responses to changes in humidity. Secondary organic aerosols (SOA) continue to receive a great deal of attention due to their impact on radiative forcing, mainly through the indirect effect (1). Ambient aerosol typically contains a significant organic fraction, arising from the oxidation of volatile organic compounds (2). SOA has been largely thought of as existing as a liquid phase, or as a combination of a solid phase within a liquid droplet, but the reality is likely to be far more nuanced. Recently, Virtanen et al. demonstrated that ambient SOA particles can have similar mechanical properties to crystalline ðNH 4 Þ 2 SO 4 particles at 10-20% RH but exist as amorphous glasses to low relative humidity (RH) rather than forming crystalline phases (3). This picture is consistent with the conclusions of Mikhailov et al. (4) and Zobrist et al. (5), who suggested that the existence of glassy states may have profound consequences for the properties of atmospheric aerosol particles, particularly at low temperatures.The term glassy refers to an amorphous, highly viscous state with a dynamic viscosity (η) of greater than 1 × 10 12 Pa s and the mechanical properties of a solid (6). In thermodynamic terms, a glass is in a nonergodic metastable state...

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“…Single droplet processes such as whispering gallery modes 26 and surface enhancement effects 27 may have significant influence on these yields, although for aerosol applications these 50 µm droplets are rather large. Nevertheless, the study of single aerosol droplet photochemistry is an application of this technique, and can be easily extended to incorporate tunable photon sources.…”

Section: Methodsmentioning

confidence: 99%

Rapid Profiling of Laser-Induced Photochemistry in Single Microdroplets Using Mass Spectrometry

et al. 2014

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Rapid assessment of laser-induced photochemistry in single microdroplets is afforded by on-demand microdroplet generation coupled to a commercial ion-trap mass spectrometer. Single microdroplets (diameter 50 μm, 65 pL) fall on a steel needle held at +2 kV where they subsequently form a spray that is directed toward the inlet of an ion-trap mass spectrometer. It is demonstrated that single microdroplet mass spectra are recordable, one at a time, for methanol droplets containing 100 μM 4-iodoaniline. Extending on this, to probe laser-initiated photochemistry in single picoliter volumes, a UV laser pulse is timed to intercept the droplet before hitting the needle. Comparison of laser-on and laser-off mass spectra reveals the laser-initiated photochemical products. We demonstrate the technique by following UV laser initiated chemistry in methanol droplets containing 4-iodoaniline and 3-(iodomethyl)-N,N,N-trimethylbenzenamine and reveal numerous products within a few hundred single droplet experiments over several minutes. This technique allows for rapid detection of laser-initiated photochemistry in single picoliter volumes. AbstractRapid assessment of laser-induced photochemistry in single microdroplets is afforded by ondemand microdroplet generation coupled to a commercial ion-trap mass spectrometer. Single microdroplets (diameter ~50 µm, 65 pL) fall on a steel needle held at 2 kV where they subsequently form a spray that is directed towards the inlet of an ion-trap mass spectrometer.It is demonstrated that single microdroplet mass spectra are recordable, one at a time, for methanol droplets containing 100 µM 4-iodoaniline. Extending on this, to probe laserinitiated photochemistry in single picolitre volumes, a UV laser pulse is timed to intercept the droplet before hitting the needle. Comparison of laser-on and laser-off mass spectra reveals the laser-initiated photochemical products. We demonstrate the technique by following UV laser initiated chemistry in methanol droplets containing 4-iodoaniline and 3-(iodomethyl)-N,N,N-trimethylbenzenamine and reveal numerous products within a few hundred single droplet experiments over several minutes. This technique allows for rapid detection of laserinitiated photochemistry in single picolitre volumes.3

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Cavity enhanced droplet spectroscopy: Principles, perspectives and prospects

Cited by 160 publications

References 116 publications

Dielectric microcavities: Model systems for wave chaos and non-Hermitian physics

Dielectric microcavities: Model systems for wave chaos and non-Hermitian physics

Comparing the mechanism of water condensation and evaporation in glassy aerosol

Rapid Profiling of Laser-Induced Photochemistry in Single Microdroplets Using Mass Spectrometry

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